Hybrid Powertrain Lash Crossing Control via Clutch Disconnection
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Solution Overview
Problem
In hybrid vehicles, drivability is compromised by torque disturbances known as lash or backlash, which occur when the powertrain transitions from positive to negative torque, causing noise, vibration, and harshness due to gear separation and reengagement, leading to clunk noises perceivable to occupants.
Innovation Solution
A strategy involving the disconnection of the engine from the driveline during anticipated lash crossings, allowing the motor to control torque and operate in speed control mode to reduce driveline disturbances, leveraging the superior torque accuracy of the electric machine to quickly and smoothly navigate the lash zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is connected to the driveline during torque reversal, then the engine can provide continuous power, but torque disturbances and lash occur due to gear separation and reengagement
Solution Approach 1:
The patent extracts the engine from the driveline connection during torque reversal events by opening the clutch. This isolates the engine torque inaccuracies that cause lash and noise, allowing the electric motor to independently control torque through the lash zone without engine interference. The engine is taken out of the powertrain connection precisely when torque reversal is detected, eliminating the harmful gear separation and reengagement disturbances.
2Power
If the clutch remains closed during lash crossing, then engine torque can be maintained, but the superior torque accuracy of the electric machine cannot be utilized to reduce driveline disturbances
Solution Approach 1:
The patent replaces the mechanical engine torque control system with an electric motor torque control system during lash crossing events. The electric motor, with its superior torque accuracy and controllability, takes over torque management when the clutch is open. This substitution allows precise modulation of torque through the lash zone, eliminating the torque inaccuracies inherent in mechanical engine systems during reversal events.
3Manufacturing precision
If the engine is disconnected during lash crossing, then torque accuracy improves and driveline disturbances reduce, but the engine cannot contribute to power delivery
Solution Approach 1:
The patent implements dynamic clutch control that opens and closes based on real-time torque reversal detection. The clutch is dynamically switched to disconnect the engine only during the brief lash crossing event, then reconnected when torque reversal is complete. This dynamic operation allows the system to optimize between torque accuracy (when disconnected) and power delivery capability (when connected), adapting the powertrain configuration to the immediate operational needs.
Data Source
AI summary
A vehicle is disclosed having a motor and engine selectively coupled to the motor via a clutch. The vehicle includes a controller configured to, in response to a vehicle wheel torque reversal, open the clutch to disconnect the engine from the motor, command the engine to enter a speed control mode, and control a motor output torque through a region surrounding the vehicle wheel torque reversal to reduce torque disturbances in a vehicle driveline.